This invention relates to liquid ring pumps, and more particularly to liquid ring pumps with rotating lobe liners.
Liquid ring pumps are well known as shown, for example, by Bissell et al. U.S. Pat. No. 4,498,844. In most such pumps a rotor is rotatably mounted in a stationary annular housing so that the rotor axis is eccentric to the central axis of the housing. The rotor has blades which extend parallel to the rotor axis and which project radially out from that axis so that the blades are equally spaced in the circumferential direction around the rotor. A quantity of pumping liquid (usually water) is maintained in the housing so that as the rotor rotates, the rotor blades engage the liquid and form it into an annular ring inside the housing. Because the housing is eccentric to the rotor, the liquid ring is also eccentric to the rotor. This means that on one side of the pump (the so-called intake zone), the liquid between adjacent rotor blades is moving radially outward away from the rotor hub, while on the other side of the pump (the so-called compression zone), the liquid between adjacent rotor blades is moving radially inward toward the rotor hub. A gas intake is connected to the intake zone so that gas to be pumped is pulled into the spaces between adjacent rotor blades where the liquid is moving radially outward. A gas discharge is connected to the compression zone so that gas compressed by the liquid moving radially inward can be discharged from the pump.
It is known that a major cause of energy loss in liquid ring pumps is fluid friction between the liquid ring and the stationary housing. Energy loss due to such fluid friction is proportional to the square or an even higher power of the velocity difference between the liquid ring and the housing. To reduce such losses, it has been proposed to rotate the housing about its central axis as the rotor rotates about the rotor axis (see, for example, Stewart U.S. Pat. No. 1,668,532). Of course, the gas intake and gas discharge must remain stationary. This leads to some complex and costly structures, and has not proven commercially viable.
Another approach to reducing fluid friction losses of the type described above has been to provide a simple, substantially cylindrical hollow liner inside the outer periphery of the housing (see, for example, Russian patent 219,072). The housing is stationary, but the liner is free to rotate with the liquid ring. Liquid is free to flow into or is pumped into an annular clearance between the liner and the housing. Accordingly, the liner, which is propelled by the fluid drag on its inner surface, tends to rotate at some velocity less than the liquid ring velocity. If the liner velocity is half the liquid ring velocity, the fluid friction energy loss between the liquid ring and the liner is one quarter (or less) of the energy loss with no rotating liner. The fluid friction in the clearance between the rotating liner and the stationary housing--in equilibrium with the drag on the inside surface of the liner--determines the actual velocity of the liner.
While the known rotating liner structures are simpler than rotating housing structures, the known rotating liner structures are not believed to reduce fluid friction losses as much as rotating housing structures.
It is therefore an object of this invention to provide improved liquid ring pumps.
It is a more particular object of this invention to provide liquid ring pumps with reduced fluid friction losses.
It is a still more particular object of this invention to provide liquid ring pumps with rotating liners which are nearly as simple as the known rotating liner liquid ring pumps, but which have lower fluid friction losses than the known rotating liner pumps.
Liquid ring pumps are practically applied in many industrial processes in which the pumped substance may be contaminated. A practical problem with liquid ring pumps with the known rotating liner structures in such environments is that there is a high probability that the annular clearance region outside the liner will become contaminated with dirt or other solid contaminants from the liquid ring. Providing a flow of clean flushing liquid in the clearance area requires both a high pressure and a high flow rate to effectively keep the annular clearance purged.
It is therefore another object of this invention to provide liquid ring pumps with rotating liners which are easier to keep purged of contaminants and which require less pressure and less flow to purge contaminants from the running clearances.